In many hot water supply systems, such as ones used in homes, the start of hot water consumption mostly includes loss of immense amount of water, inconvenience and even chill during waiting for hot water arrival to the tap.
In known immediate hot water delivery system, hot water line from the heater to the tap is kept from chilling by circulation or by reciprocation of hot water between hot and cold water pipes.
Closest patent based on circulation principle is aspirator water circulation apparatus disclosed in European Patent Application EP 0 809 079 A1. U.S. Pat. No. 6,026,844 is related to storing hot water in an insulated reservoir and after the stored volume returns to the system, storing is repeated. U.S. Pat. No. 6,227,235 teaches a reciprocate circulation of water between hot and cool lines. Main disadvantages of commercially available circulation and reciprocation instantaneous hot water delivery are high production cost, high electricity consumption, and poor service characteristic. No analogues based on heat transfer along hot water lines have been found.